Rõngu (German: Ringen) is a small borough (alevik) in Elva Parish, Tartu County, southern Estonia.

The present-day ruins are the visible remains of a so-called "vassal castle", i.e. a smaller fortress not designed for major military operations, established in the early 14th century.

The gate, the remains of which are most prominently visible today, was strengthened by a gatehouse that also housed a chapel on its second floor.

The Jesuits however blew up the castle amid the events that led to the Truce of Altmark and the subsequent incorporation of the area into Swedish Livonia.

The church seen today is a heavily rebuilt Neo-Gothic edifice which received its look during the late 19th century.